Photoablative Nd: YAG-laser goniotomy enhancing trabecular outflow facility in porcine cadaver eyes.

Abstract

Mid-infrared laser technology opens new perspectives in experimental glaucoma surgery. The aim of this study was to investigate the potential effectiveness of photoablative Nd: YAG-laser goniotomy in increasing trabecular outflow facility as a surgical alternative to conventional goniotomy. Eye cups of 19 freshly enucleated porcine cadaver eyes were fixed in an anterior-segment perfusion system, and outflow facility was measured under constant pressure conditions (7-13 mmHg) over a period of 45 min. Trabecular laser goniotomy was performed using a continuous-wave Nd: YAG (1.06 microns) laser. Radiation (1.8 J) was delivered in several pulses (200 microns) through an articulated delivery system. Photoablative Nd:YAG-laser treatment yielded reproducible ablation zones, with the depths varying between 600 and 750 microns. Collateral thermal damage extended to a depth of 130-260 microns. Outflow facility measurements revealed an increase (mean +/- SD) from the baseline value of 0.128 +/- 0.041 microlitter mm Hg-1 in control eyes (n = 11) to 0.366 +/- 0.128 microlitter min-1 mm Hg-1 in treated ones (n = 8). Application of photoablative Nd: YAG-laser goniotomy yielded reproducible ablation zones within the anterior-chamber angle, resulting in a significant reduction (72%) in outflow resistance in perfused anterior segments of freshly enucleated porcine cadaver eyes. Contact low-thermal laser goniotomy might offer a feasible alternative to surgical goniotomy.